Aluminum alloy



without heat treatment.

Patented July 14, 1942 i Ohio, in i No Drawing.

The National Smelting Applicat Serial No. 431,680

Company, Cleveland,

a corporation of Ohio:

oil-Fe ruar 20, 1942,

a: 8 Claims; (01. 75-9146) This application is a continuation-in-part ofmy copending applicationserial No. 389,020, filed April.1'7, 1941. andparticularly to aluminum y I able for casting and working, and havinghigh strength at ordinary and elevated temperatures.

It is an object ofethis invention to produce base alloys suit;

The invention relates to-alloys,

alloys having relatively high elongation and 'relartively high tensilestrength. i, I

It is a further object of this inventionto pro vide a relatively lightalloy whichmay be easily cast and machined, which may bet used at elevated temperatures without a rapid deterioration of desirableproperties, and which may be readily treated with anodic treatmenttogive excellent lustre andfinish. i v r v M t It is a still furtherobject of this invention to provide an alloy having a rel atively highpropor-f tional limit and relatively high fatigue strength, and in whichthese properties may be obtained by" the formula should lbe presentcombinewith the When magnesium and aincl are added aluQ minum in theproperproportionsa ternary co nrelative to each preferably the ratio ortion in the aluminum,

pound of aluminum, agnesiumand zinc is formed, whichompound]isfsolublefin fsolid solu- Theg presence of this com-; pound in"a relatively. small amountgreatly: im

proves the characteristics'oi aluminum and produces an alloy having highstrength combined with high ductility, good casting, rolling, extrud ingand forging properties, good color and. eitcellent corrosion resistance.ln calculating the amount of magnesium and zinc that should be presentin the aluminum alloy to form the desired percentage of ternarycompound, only magwnesium which is not combine'd'with silicon is to becalculated, as it' is only such magnesium that formula having-thegreatest proportion of zinc, increases the brittleness and decreases thedue: tility of the alloy. For this reason it is undesirable that zinc bepresent in quantities sub:- stantially greater than the amount to reactto form such a ternary. compound with magnesium and alumlnum.- The mostdesirable properties are obtained when the magnesium and the zinc areproportioned so that the ratio of magnesium (uncqmbined withvanysilicon) to zinc is about equal to the ratio, represented by the formulaAhMs=zm,;or somewhatflareer, as represented i AlsMgvZIlo. A small-amountof magnesium may i that may occur when the alloy metal Magnesium addsing qualities of remelted. to the hardness and machinthe alloyand, asabove stated, [in an amount suflicient fto zinc and aluminum present.Ingreater quantities, magnesium tends to make the alloy sluggish,decreasing castability.

The improvedaluminum alloys may have the ternary compound of aluminum,zinc and magnesium present in an amount ranging from about 1%yor 2% to20%,the preferred range being between about-3% and 15%. At roomtemperaurns ternarycompound goes-into solid solution inaluminum alloysin an amount of about 2%. "lThepercentage insolid solution increases athightemperatures and decreases upon cooling, the excess precipitatingout. Aluminum alloys containing the ternary compound may, therefore, beadvantageously heat'treated to improve their properties.

is available to combine with zinc and aluminum to form the'ternarycompound.

The ternary compound is said bysome investi; gators to have acomposition having substan-, tially the formula AlaMgizna, and otherinvestigators'have considered theformulaforvthe ter nary compound asbeing AlzMEaZllaQ It will be seen that the amounts of magnesium and zincother are quite similarinboth formulae The magnesium andl zinc should bepresent in about the proportion necessary to form the ternary compoundof either formulae, or} the magnesium to zinc in the alloy should bebetween the ratios in the formulae; l l in .7

An excess .of zinc, over and above that gwhich' cooperates withmagnesiumand aluminumhto form a ternary compoundfaccording to the abovei or silicon combining ,A small amount of silicon is usually present inaluminun alloys'and upto 1.5% silicon may be present in the alloys ofthe present invention. It the'alloys are to be rolled or worked thesilicon should below, from about the minimum obtainable quantity of5.04% or .05% to about 11%. More than 31% isfrequently desirable incasting alloys; Silicon combines preference to most elements, each partby weight weight, of magnesium rto form MgzSi. At least sufficientmagnesium istherefore added to the alloy to combine with the siliconuncombined with any calcium to form MgzSi, and in addition tocombine.with all the zinc and form the ternary compound according to the formulaAlzMgaZna.

[ MgzSi is more stable than the ternary compound be maintained in solidalloys in an amount up is th quantity of MgzSi ispresent in the alloy,and

solution in aluminum present if the silicon above mentioned and may toabout 1.85%, w ch be provided to replenish losses with magnesium inwlth'about 1,75 parts; by I Although it does not desired in a given inconjunction with the ternary compound. MgzSi does not, however, make aseflicient use of the magnesium as does the above mentioned ternary.compound. Therefore, it i desirable to have the magnesium present on therich side to prevent the silicon being present in excess and takingmagnesium nary compound,

It has now been found that aluminum alloys containing magnesium (overthat necessary to combine with silicon) and zinc in the proportions awayfrom the termanganese and 'Alloys containing manganese may" be readily 7heat treated or age hardened to' give somewhat superior properties;butvery 'desirable properties are obtainable"whe n castings are simplyaged at room'temperaturejonwhen quenched from themold and age QManganese is a very efie'c'tive element in the alloy and desirableimprovements are noted when about .1% or even a little less, such as.05%,' is presentin the alloy. The preferred properties areobtained'with about .'2%' to about 5% or .8% manganeseyand in'som'ecases it is desirable .to have the manganese present as about 1%, oreven 1 .5%.

Chromium is a particularly effective alloying element in the alloy. ofthe presentinvention.

' appear to improve the roportional limit and yield strength of thealloy sistance. It is, therefore, particularly advantageous that bothchromium and manganese be present. As little as .05% or .1% chromium,particularly with manganese, is effective in improvin'gthe properties ofthe alloy,'but .2%' 'or .3% to about 1%, or even 1.5%, is desirable.manganese is also present, thetotal of manganese and chromium shouldpreferably be between about .3% and 2.5%of the alloy.

The quantity of each of the hardening metals compound and it is,therefore, preferred to; havea larger percentage of the present, such as4% to 8% may be present.

acts as a hardener which is sometimes desirable purposes, 9% ternarycompound containing about 5.4% zinc. When the casting is more or lessintricately shaped, still greater percentages, such as 10% to 12% or15%,,of the ternary compound For alloys to be forged or shaped aftercasting, the ternary compound should be present in the lower ranges,such as or so, as the metal is less hard with the ternary compound.

I v refining metal such as is set forth in the above group, is improvedby the presence of iron in suitable proportion.

ternary compound Iron in suitableamounts further increases the hardnessand tensile strength are aged at room temperature without a heattreatment or quench- 1 duetiiity' fingering-nee du nt z d'eSimme-manamminumi ano i eomgming i ron;

nuni allo be present n h n ofethes me fiswlpre e-is 40 1 o isho s n s meev' the naep m rbpdrtiqn'tq comb-me wnhthe silicon and "t0" orin.1 oi"the ternary 1 compound 2' AlsMgqzne, with"the balance substantially amminum and minor impurities was prepared and hi eesi ntote i; 3 7 1 n ehe n e Seven aaysgau .rqomrtefiiper mre.whe tested they properties of"the anew, the man um and grain refining" elements w ther improvementindependent? v The alnminfilinf allpysggqf the tiqn eontaining" magnesisilicon, and zinc in' e cbmpound'; when east 1"] M I that chillingtakeis'jlacefsq ta y, nebusly in the Lvariqus fbottiqn's of the19,000'1bs./sq.'in. the hardness was '80 Rockwell chilling may not be lys re m er ol tween?" esi fiin 7 bor'on m-th amoumonp0 ;to1.1 coniiimast 1; rs were quenched and n a re lower a q tnegeastability is decleased 'wExa mpZea3-- a w n w n w, a wnenwhe'ial dyoiniahlpleziontainedxoava 9? 0 t e mrefine ee e t heme;vanaamnrmsmm-,zorymhgsfiefi; the test bars we W T 53 93 0? F 29? 45which were"emueast,fqumnenmagedseven f m of r fi s s e n W33 SFa P Qdays at mamtembeiawr new hardness of '14-, d p 4 9 QW FF EP E WWW??? w man '-1Qnat'1QiigQrsW; a. brobdrtional limit or mustbe t s ed- Th exa urne i el c ei 16600 lbs/sci; a Mad strength 6: 24,900 r m the grounv syeE' WF PmJ D SR Q tensilestength of 38300 m percem rnolybdenum, "zijxegnium and yanadijum"; .and of Vanadium m me aneSs-wasso, the

peeiany tungsten am} nielypljd'en th 0 mean lixnit was the strength andd 'trength 1was25500 'th was 40,400

v w elqeeieeq w HROOW -l e swine used, b'utfwhen 'sfiecial pro-perms I Igated article are" important it. desyraple Itd se lect} e in" r fln rih'e 1 1 9 fl li e' en SQ ILP OPQ S?T5 3 lumbilim and'l tantal mgmTitanimnbeing .r

- When man alloy Of Exam le 2' the when qu nch ewand aseeeve d y' t: oome "The abdv'e' descrihed handeniing e ganese and ehl ominni;substantially d r e-leh- J 1" thegy dgst e gth was 25,800 lbs/sq. imi'and thq tensilestrength was 42,000 lbs./ sq. in. wnen thegtestbars-wexge simply air cooled and aged seven days at room temperature,the elongation was 9.3%, the px opprt'lonal limit was 18,200 1bs./sq.in, the yield strength was 25,800 1bs'./-sq. in and the tensilestrengthwas 40,600 5% t f I 1b$. /sd."in. When the molybdenumawas increased a gj 7 A v 1' td.-'12%;test bajrs whichwere-chill cast, quenched ,7 f-endagedsevendaysfatif Itemperature had'an e1ongation* "of*121%," a.prbportional limit of 16,700 lbssq. in., a yield strength of 24,500lbs./sq. 75 in., and a tensile strength of 41,400 lbsjsq- 1 T thepresent invention:

tune was 11 .2%, theprqpprtional limit wa s 18,100

the amount Example 5 and the hardness was,80 Rockwell E.

Example 6 Sand cast test bars were prepared from an al-- loy having thecomposition of about 1.8% magnesium, about 3.5% zinc, about 28% silicon,about .5% iron, about 28% manganese, about .3% chromium and about .2titanium and aged seven days at room temperature. These; bars had atensile strength of 33,300 lbs/sq. in., a proportional limit of 14,700lbs/sq. in., a yield strength of 21,400 lbs/sq. a hardness of Rockwell E72.5 and'an elongation of 6.2%.

Example 7 An aluminum base alloy containing magnesium, zinc andsiliconin proportions to form 6% of a ternary compound, based on the formulaAlr'MgvZnc, .6% iron, .25% chromium, .2% titanium and .3% manganese wasprepared. Test bars made from this alloy, quenched from the mold andaged seven days at room temperature, 7

had a tensile strength of 42,300 lbs/sq. in., a

strength of 24,300 lbs/sq. in., a hardnessRockwell E 80.8 and anelongation of 10.3%. When of manganese in the same alloy was increasedto .5 similarly prepared and treated test bars had a tensile strength of41,600 lbs./sq. in., a proportional limit'of 17,600, lbs./sq. in., ayield strength of 23,500 lbs/sq. in., a hardness of Rockwell E 801 andan elongation of 9.6%. When manganese was present in the amount of about35%, test bars similarly prepared and treated had a tensile strength of41, 00 lbs/sq. in., a proportional limit of 18,400 lbs/sq. in., a yieldstrength of 24,300 lbs/sq. in., a'hardness of Rockwell E 80.5 and anelongation of 8.4%.

'When manganese was present in the amount of 1%, test bars similarlyprepared and treated had a tensile strength of'39,900 lbs/sq. in., aproportional limit of 19,000 lbs.'/sq. in., a yield strength of 25,900lbs/sq; in., a hardness of Rockwell E 81.1 and an elongation of 5.9%.

Example 9 Chill cast impact test bars of the standard V- notch andkeyhole types were prepared from an aluum base alloy containing 6% ofthe ter- .25% manganese, .6% iron,

at room temperature, elevated temperatures and low temperatures.

Copper is frequently an impurity in aluminum alloys and, unlike thehardeners present in alloys of the present invention, copper is aprecipitation hardening ingredient which is much more soluble at hightemperatures than at low temperatures. Substantial amounts of copper aredesirable when the alloy is to be solution heat treated. Alloys of thepresent type containing copper in an amount of more than .1 or so formthe subject matter of copending applications.

Since the molecular proportion of zinc is never more than the molecularproportion of the relatively light magnesium in the ternary compound, itis seen that in addition to high strength the alloys are light in weightand are, therefore, especially adapted to aircraft construction and thelike. This is particularly true when the quantity of ternary compound issufliciently low so that the alloy may be drawn or rolled intostructural members.

If the alloy contains uncombined silicon, about 1.75% magnesium isrequired to combine with each percent of uncombined silicon to formmagnesium silicide (MgzSi) before any ternary compound will be formed.For example, if 2% of the ternary compound on the basis of AlzMgaZm bedesired in an alloy having .3% silicon, the amount of magnesium to beadded to form the ternary compound will be 45%, or about .5%, and themagnesium to, combine with .3% silicon will be about .5%, making a totalof about 1%.

The magnesium and zinc in an alloy containing .7% free silicon and 20%A13Mg'lZn8 would be about 7% and 12%, respectively. The alloys describedherein include aluminum, magnesium and zinc, the magnesium, uncombinedwith silicon, being proportioned to the zinc in the ranges of theformulae given for the ternary compound. The proportions for theformation of the ternary compound in the alloy exist when the magnesiumis about 35% to 45% of the zinc content plus of the silicon content.Most desirable properties may be obtained when the magnesium (uncombinedwith silicon) is in the lower portion of this range, or about 35% to 40%or! the zinc.

A very astounding fact has been discovered, however, in connection withthese alloys, namely, that the tensile strength may increase up toapproximately 50% Olf its initial value by aging at room temperature forrelatively long periods of time, such as a few months. The sameimprovement in tensile strength can, of course, :be obtained relativelyquickly by aging at temperatures abo've room temperature.

To obtain properties even of, the same order of so that they can berolled or rods, wire, structural shapes, castings machine ,sults, andare lution heat treat for improvement in properties. The alloys of thepresent invention have good fatigue and tensile strength and arelatively high to be heat treated if it is although such heat and theyhave sufiicient treatment is not required; ductility and hardness.formed into sheets,

parts, etc. These alloys "have a desirable color, high corrosionresistance, and may beanodically finished or highly polished withexcellent resuitable for many uses, among them being the production ofcastings which are shaped or formed to someextent after castingspercentages of ter- The, alloys having the lower nary compound may evenbe forged at room temperature and are thus. useful for many specialpurposes. l

It is to be understood that, in considering the 1 amount of zinc andmagnesium to add to alu- 1 minum alloys to form of aluminum, magnesiumand zinc in the alloy,

the ternary compound such magnesium as is necessary to combine with theunoombined silicon is not to be considered 1 as part of the magnesiumnecessary to form the specified amount of ternary compound.

As pointed out above, grain refiners are usually desirable in alloys ofthe present invention. However, it. has been foundv that the alloys ofthe present invention have relatively high base alloy containing magesilicon in an amount up grain refining metals to 1.5%, and one or moreproportional limit, even at relatively high temp peratures; they havedesired to improve and modify their'properties, content, the totalmagnesium strength, high proportionallimit and ductility withoutsolution heat treatment,-even in the ab- .1% to about 1.5% iron,manganese, about .05% to nesium, zinc,

with the balance substantially all aluminum and minor impurities, theamount of zinc in the alloy being about .6% to about 9%.and the amountof magnesium in the alloy uncombined with silicon being about to aboutof the zinc being within the range of about .5% to about 7%.

2. An aluminum base alloy containing magabout .1% to about 1.5% iron,about .05% to 1.5% manganese, about .Q5% to about 1.5% chromium, siliconin an amount up to 1.5%, and one or more grain refining metals in atotal amount of about .005% to about .5%; with the balance substantiallyall aluminum and minor impurities, the amount of zinc in the alloy beingabout .6% to about 9%, and the amount of magnesium in the alloyuncombined with silicon being about 35% to about 45% of the zinccontent, the total magnesium being within the range of about .5% toabout 7%.

'3. The alloy set forth in claim 1 in which the zinc content isabout1.2% to 6% and the magnesium content is within the range of about .5% to6%.

4. The alloy set forth in claim-l in which the zinc contentis about 1.2%to 4.3% and the magnesium content is within the range of about 5% to 5%.

5. The alloy set forth in claim, 2 in which titanium is present intheamountof about ,05% to .5%. y i

6. The alloy set forth in claim 2 in which molybdenum is present in theamount of "about 01% to .5%. l i .7. The alloy set forth conium ispresent in the amount of about .05% to .5%. i

8. An aluminum base alloy containing magnesium, zinc, about .1% to about1.5% iron,

about .05%. tov 1.5% manganese, about .05%

-,the amount of zinc in the alloy being about 6% to about 9%, and theamount of magnesium in the. alloy uncombined with silicon being about25%. to about 45% of the zinc content,

,the total magnesium being within the range of about .5% to about 7%..

WALTER. BONSACIGI.

in claim 2 in which zir-v

